The invention relates to a phase indication device of a sewing machine, and more particularly to a device for electrically indicating an optimum phase of the sewing machine for starting the sewing machine for a stitching operation.
It is generally required that the sewing machine is set in a predetermined optimum phase for starting the sewing machine for a stitching operation. If the sewing machine is started with a lagged starting phase the thread take-up lever will not suitably tighten the seams, resulting that the slackened seams are produced and that the jamming at the loop-taker is caused due to the slackened thread. On the other hand, if the sewing machine is started with an advanced starting phase the upper thread may be drawn out of a needle hole due to the upward movement of the thread take-up lever.
Hitherto, for preventing such undesirable phenomena, a drive motor with a brake device has been used to stop the sewing machine at a predetermined optimum phase at which the sewing machine is started again for the next stitching operation. Such a drive motor is, however, very expensive and disadvantageous for a massproduction of the sewing machines.